Electric transformer



Oct. 5,1926. 1,602,001

8. 2. DE FERRANTI ELECTRIC TRANSFORMER Filed Feb. 11', 1926 I 1 vb I 1 Fig.5. Fig.4. 5.1::22 Emma INVe NTOK Patented Oct. 5, 1926.

UNITED STATES PATENT OFFICE.

SEBASTIAN ZIANI DE FERRANTI, or HoLLINwoon ENGLAND, assrenon ro FER- RANTI, LIMITED, or nommwoon, nnenann.

ELECTRIC TRANSFORMER,

Application fi led February 11, 1926, Serial No This invention relates to electric transformers and more particularly to small audio frequency transformers for use in connection with wireless telephony, and has for its object to provide improved or simplified constructions.

Referring to the accompanying diagrammatic drawings Figure 1 is a vertical sectional view of a convenient construction in accordance with the present invention.

Figure 2 is a vertical sectional view taken at right angles to that according to Figure 1. I y

Figure 3 is a side elevational View with one of the primary terminal nuts removed for clearnessr Figure l is a plan View.

In carrying the invention into ellect in one form by way of example, I form a casing of two identical pressings a, a, of thin sheet metal, these pressings being formed with rims l), b to impart lateral rigidity. To the base of each pressing two further pressings 0, c of channel shape and of preferably heavier gauge metal are attached, conveniently by spot welding or riveting, the casing pressings bein reinforced at this region by means of angle pieces at, d also spot welded or riveted. to the casings. The

two pairs of channel pressings serve as feet for supporting the casing, and each is per forated at e, e. The core comprises a pin rality of laminae f, which when erected form one central limb and two return limbs, those on the outer sides of the core being slightly smaller than the inner ones (see Figure 2) first to enable the center'limb of the core to pass through. the circular or approximately circular hole through the bobbins and also to enable the core to it within the casing which at the corners has a radius; if the stampings were all of the same size at the exterior the casing pressings would require perfectly square corners. The primary and secondary windings of the transformer are disposed upon the central limb, each winding being preferably formed of four separately wound bobbins connected in series electrically. A connecting lead is taken from the two extreme ends of the primary and seconda windings. The primary leads are connected respectively to two terminals mounted in a primary terminal block 2, and the secondary leads are similarly connected 87,690, and in Great Britain November 6, 1924.

through its entire'length, to enable the leads to bs brought through these holes and to be soldered'finally at g to the tips of the terminals. One limb of eachstrip is adapted to rest behind a few of the outermost core laminae, and thus to support the terminalbloclrs flush against the outermost core iamlnae,a sheet of insulating material 7 being interposed at this point as regards the secondary terminal bloclr but as regards the primary terminal block I insert at this point a condenser s appropriate to the characteristics of the transformer and the uses to which it is to be put. This condenser conveniently comprises two or more thin conducting plates separated by a sheet of dielectric material and each provided with a cranked A further sheet oi insulating materialis rovided above and below the thin conducting plates and each of the tangs is slit for the insertion oi? and soldering thereto of the conducting leads from the two ere treme' ends or the primary winding. The condenser as air hole is bound with a sheet of paper or the like and is inserted between the primary terminal block Z and the outermost core laminae which this bloclr abuts. The moulded terminal bloclrs are thus provisicnally attached, to the transformer 'proner being permanently connected to the windings by short leads the moulded blocks and ter .ninals and condenser (if used) bein all finally clamped firmly together and held in position by the casing when the latter is clamped together.

the terminals may moulded in individcal blocks or preferably in common blocks as regards primary secondary and are so arranged that a portion portions of the insulation projects or project through holes M the casing, these portions thus insulating the terminal stems a sufliciently long leakage Alternatively,

the condenser may be moulded in the primary terminal bloclr ina. sale stead of being fitted behind it as described above.

Each casing pressing a, a is formed with two openings which enable these pressings to be applied back to back and being so arranged that the four terminals and portions of the terminal blocks protrude through the holes. The two casing pressings are clamped together by bolts 8 and nuts t. The bolts, however, do not require to pass through the core laminae and when bolted together the pressings not only clamp the laminae firmly, but also clamp the terminal blocks and prevent any possible displacement thereof.

It will be understood that when so clamped the thin supporting strips have no function, being provided solely as temporary supporting means prior to the fitting of the pressings. The casing portions, however, may be removed entirely to give access to the transformer proper without disturbing the terminals, connecting leads and primary shunting condenser (if provided).

After the transformer has been erected I prefer to attach a number plate (not shown) within the channel formed by one of the pairs of feet, this conveniently being effected by means of eyelets, the number plate besides providing means of identifica tion serving to prevent the transformer from being dismantled without breaking of the number plate.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is 1. An audio frequency electric transformer embodying a self-contained unit i11 eluding a laminated core, coils on said core, terminal blocks connected to said coils and provisionally supported by the lamina of said core and a two-part perforated metal casing, which latter when clamped in position entirely encloses and maintains said unit rigidly in position with the terminals projec-tlng through perforations in the casing parts.

2. An audio frequency electric transformer as claimed in claim 1, wherein the two-part perforated metal casing comprises thin sheet metal pressings to which are fastened channel feet of preferably heavier gauge, the pressings being reinforced at the regions of attachment of the feet.

3. An audio frequency electric transformer as claimed in claim 1, including an appropriate condenser incorporated as part of the self-contained unit.

In testimony whereof I have signed my name to this specification.

SEBASTIAN ZIANI on FERRANTI. 

